We have developed a system to simplify study of human cell-surface structures by procedures which permit study of antigens due to individual chromosomes. A human-Chinese hamster somatic cell hybrid which contains chromosome 11 as its only human chromosome has been produced. This hybrid which expresses human cell surface antigens has been employed as a model system to study these components using a combined immunological, biochemical and genetic approach. This system has enabled us to do regional gene mapping of these antigen markers, of enzymes coded for by chromosome 11, and of the beta-globin gene complex. Studies of this kind should make possible rapid and definitive identification of a large variety of human cell-surface antigens which may influence malignant behavior of human cells. The chromosomal location and biochemical identity of such genetic determinants may help elucidate genetic relationships of antigens involved in the malignant response.